CN110658130A - Device and method for measuring friction coefficient of tenon joint - Google Patents
Device and method for measuring friction coefficient of tenon joint Download PDFInfo
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Abstract
The invention provides a device and a method for measuring the friction coefficient of a tenon joint, wherein the device comprises a bottom plate, a steel wire rope, a balance weight, a test piece groove, a steering mechanism and a testing machine interface for connecting a mechanical testing machine, wherein one end of the bottom plate is provided with the steering mechanism, the other end of the bottom plate is provided with the test piece groove for accommodating a test piece to be tested, the balance weight is arranged on the test piece to be tested, one end of the steel wire rope is connected with the test piece to be tested, and the other end of the steel wire rope bypasses the steering mechanism to be connected; the device and the method for measuring the friction coefficient of the tenon joint can realize quick, effective and accurate measurement of the friction coefficient of the tenon joint, are reasonable in structural design and convenient to operate, can effectively reduce measurement errors, enable the measurement errors to be in a minimum range, are low in cost and are beneficial to use.
Description
Technical Field
The invention relates to a device and a method for measuring a friction coefficient of a tenon joint.
Background
The tenon joint is widely used as a main connecting mode of traditional solid wood furniture in China, is famous for exquisite appearance and firm structure, does not adopt any metal hardware and adhesive, and can achieve ideal joint strength only by the close fit between the tenon hole and the tenon, and the process is still used. The stress condition of the tenon joint furniture is various, but the mechanical property of the tenon joint furniture can be generally considered to be the pull-out resistance, the bending resistance, the torsion resistance and the like, and the three strengths are related to the pressure and the friction coefficient at the joint of the tenon joint.
Under the mode of non-glue tenon-and-mortise joint, the pulling strength of the tenon joint is completely derived from the friction force between the tenon and the mortise, and the friction force is the combined effect of positive contact pressure and friction coefficient generated by interference fit between the tenon and the mortise. Therefore, in the case of a non-glued joint, the friction coefficient and the contact pressure of the dovetail joint interface together determine the magnitude of the joint strength. Meanwhile, even in the gluing process commonly adopted in the existing solid wood tenon joint furniture, the adhesive at the interference fit part is almost not existed through the observation of a microscope, and the pulling strength of the tenon joint node is still determined by the friction force between the tenon and the tenon hole and the gluing strength of the clearance fit part.
A large number of scholars research the mechanical properties of solid wood tenon joints, but mainly focus on research on factors influencing the strength of the tenon joint. The current research on the strength of the tenon joint is mainly started from the following aspects:
1) the influence of the fitting parameters on the tenon joint strength is substantially the influence of the positive node pressure on the tenon joint strength (reference 1: songshucheng, Zhulihua, Mazhen, Liuwenjin, St.I. St.J. Lin industrial, 2014,41(03): 20-23).
2) The influence of the form of the tenon joint on the joint strength was evaluated by testing the pullout and bending strengths of the different forms of tenon joint T-shaped or L-shaped members (reference 2: TANKUT A.N, TANKUT N.the effects of joint forms (shape) and dimensions on the string hs of mortises and tenon joints [ J ]. Turkish Journal of Agriculture and Forestry,2005,29(6):493 498. reference 3: intensity comparison research on several joint joining modes of plum blossom, Liu Wen jin, Sun Delin fast-growing pine furniture [ J ]. proceedings of the university of technology of south China forestry, 2014,34(2): 122-.
3) The influence of the adhesive type and different tree species on the strength of the tenon joint (reference 4: SMARD ZEWSKI J.Strength of profile-additive joints [ J ]. Wood Science and technology,2002,36(2): 173- "183. reference 5: RATNASINGAM J, IORAS F. effective of adhesive type and glue-line thickness on the surface texture joints [ J ]. European Journal of Wood and Wood Products,2013,71(6): 819. reference 6: smardzewski J.Effect of wood properties and glue type on contact stresses in atomic and tension joint [ J ] Proceedings of the organization of Mechanical Engineers Part C Journal of Mechanical Engineers Science,2008,222(12): 2293. 2299.)
Through the reference of relevant documents, the intensive research on the tenon joint from the node level is not found. The measurement of the friction coefficient only stayed in a planar contact state, and the study contents included the measurement of the friction coefficient between wood and wood, wood and rubber, and wood and a tool, etc. (reference 7: schmeijun, li, gaoxin, zhepe, the influence of grain direction on the friction coefficient between wood and rubber belts [ J ]. wood working machinery, 2012,23(05):38-42+15. reference 8: dawny, zhaxang, ludwig, lugbao, the influence of a lubricating cooling medium on the friction coefficient between tool and wood surface [ J ]. wood industry, 2012,26(05):52-55+ 59.). The existing methods for mainly measuring the friction coefficient of the wooden material mainly comprise an electronic scale measuring method, a hydraulic press method and a hydraulic cylinder method. Three methods for measuring the coefficient of friction of wooden materials are specified below:
electronic scale measurement, as shown in fig. 1, a wood (01) is placed on a wood board (02), an electronic scale (01) is connected to the wood (01), tension is measured by manually dragging the electronic scale (01), and a friction coefficient is further calculated. The method has the defect that a large error exists in the manual traction process (reference 9: Wangdan. traditional wood structure node area friction energy consumption mechanism and mechanical modeling test research [ D ]. Kunming university of technology, 2014.).
The hydraulic method mainly uses a jack or a hydraulic cylinder as a horizontal driving force, as shown in fig. 2 and 3. Wherein FIG. 2 is a jack method (reference 10: Zhangpengcheng. ancient architecture of China and its earthquake resistant development research [ D ]. Western An architecture science and technology university, 2003.). The upper end and the lower end of the first test piece (01) are respectively provided with a second test piece (02), the two sides of the second test piece (02) are respectively provided with a limiting support (03), a horizontal jack (04) and a vertical jack (05) are arranged, and gaskets (06) are respectively arranged between the horizontal jack (04) and the second test piece (02) and between the vertical jack (05) and the first test piece (01). Horizontal thrust and axial pressure are realized through the two jacks in the horizontal direction and the vertical direction, the loading mode still needs to be manual, data reading is inconvenient, the device is complex, and large errors are easy to generate.
Fig. 3 adopts a hydraulic cylinder as a driving force, a test piece (01) is arranged on a fixed base (02), a counterweight (03) is arranged on the test piece (01), a displacement meter (04) and a hydraulic cylinder (05) are respectively arranged on two sides of the test piece (01), a pressure sensor (06) is arranged between the test piece (01) and the hydraulic cylinder (05), and meanwhile, the pressure sensor and the displacement meter are added, so that the reading is more convenient, but the problem of loading speed control is also solved, and a measuring device part is separated from a loading part, so that more mechanisms are provided, and errors are easily caused (reference document 11: munqingjun, friction performance between wood materials and influence research on wood structure design [ D ]. northeast forestry university, 2010 ]).
The three methods can only measure the friction coefficient of the wood and the timber in a plane contact state, the measuring device is complex, errors caused by human factors are large, and the friction coefficient of the tenon joint in a curved surface contact state cannot be measured.
The above-described problems are problems that should be considered and solved in the measurement of the coefficient of friction of the dovetail joint.
Disclosure of Invention
The invention aims to provide a device and a method for measuring the friction coefficient of a tenon joint, which solve the problems that the measuring device in the prior art is complex, the error caused by human factors is large, and the friction coefficient of the tenon joint in a curved surface contact state cannot be measured.
The technical solution of the invention is as follows:
the utility model provides a measuring device of tenon joint node coefficient of friction, includes the bottom plate, wire rope, the counter weight, the test piece groove, steering mechanism and be used for connecting the testing machine interface of mechanics testing machine, the one end of bottom plate is equipped with steering mechanism, the other end of bottom plate is equipped with the test piece groove that is used for holding the piece of waiting to test, on the piece of waiting to test was located to the counter weight, the piece of waiting to test was connected to wire rope's one end, steering mechanism connection testing machine interface was walked around to wire rope's the.
Furthermore, the steering mechanism comprises a steering seat, a fixed pulley and a fixed bolt hole, the steering seat is provided with a steering groove, two ends of a rotating shaft of the fixed pulley are respectively connected with two sides of the steering groove, and the steel wire rope bypasses the fixed pulley and is respectively connected with a piece to be tested and the interface of the testing machine.
Furthermore, the steering seat comprises a chassis and a steering block, the steering block is arranged on the chassis, the steering block is provided with a steering groove, the chassis is provided with a fixing bolt hole and a fixing bolt, the bottom plate is provided with a screw hole, and the fixing bolt penetrates through the fixing bolt hole and the screw hole of the bottom plate to be in threaded connection with the bolt hole on the table board of the mechanical testing machine.
Furthermore, the bottom of the bottom plate is provided with a positioning interface, and the positioning interface is matched with a positioning hole in the table top of the mechanical testing machine.
Furthermore, the bottom plate is provided with a positioning groove, the chassis is arranged in the positioning groove, and the bottom plate is made of a metal plate or a hardwood composite board.
Further, the to-be-tested piece includes tenon and the mortise component that awaits measuring, and the tenon that awaits measuring is located in the mortise component, and the mortise component includes mortise upper portion and mortise lower part, and the bottom surface on mortise upper portion and the top surface butt joint of mortise lower part form the mortise jointly, and mortise upper portion and mortise lower part independent setting respectively, and on the mortise lower part was located on mortise upper portion, wire rope was connected on mortise upper portion, mortise upper portion fixed connection counter weight, and mortise upper portion does not glue by the side tenon, and the gluing of mortise lower part is by the side tenon.
Further, the to-be-tested part adopts a double-tenon structure.
A method for measuring a coefficient of friction of a tenon joint using any one of the above-described devices, comprising: comprises the following steps of (a) carrying out,
s1, preparing a tested piece, respectively processing a side tenon to be processed and a tenon hole component, and cutting the tenon hole component into two parts from the middle part, namely respectively obtaining the upper part and the lower part of the tenon hole, wherein the mass of the upper part of the tenon hole is m, and the lower part of the tenon hole is glued with the side tenon to ensure that the lower part of the tenon hole and the side tenon to be processed do not generate relative displacement when the steel wire rope is subjected to tension loading, but the upper part of the tenon hole and the side tenon to be processed are not glued, so that the upper part of the tenon hole can freely slide under no pressure, and a rivet is embedded into the upper part of the tenon hole and is used for being connected with the steel wire rope;
s2, fixing the device for measuring the friction coefficient of the tenon joint node according to any one of claims 1 to 5 with a mechanical testing machine through a positioning interface and a fixing bolt hole, ensuring that a bottom plate is horizontal, placing the lower part of a glued tenon hole in a test piece groove, fixing, then butting and assembling the upper part of the tenon hole and the lower part of the tenon hole, and placing a balance weight with the mass of M on the upper part of the tenon hole and fixing the balance weight with the upper part of the tenon hole; connecting the steel wire rope with a rivet at the upper part of the mortise, and connecting an interface of the testing machine with the testing machine;
s3, before measurement, measuring the efficiency p of the fixed pulley, and calculating the friction coefficient in the later period; during measurement, firstly, setting the loading speed of a testing machine; then, adjusting the testing machine to enable the steel wire rope to be slowly tensioned, observing the reading of the testing machine until the steel wire rope is parallel to the bottom plate and the reading of the load of the mechanical testing machine is zero, starting to measure, slowly moving the upper part of the tenon hole under the traction of the steel wire rope, recording the load value F displayed by the mechanical testing machine after the load is stable, and entering the next step;
s4, calculating the friction coefficient mu of the tenon joint node as follows:
in the formula: f is the tensile force displayed by the mechanical testing machine; p is the efficiency of the fixed pulley; m is a counterweight mass; m is the mass of the upper part of the tenon hole; g is the acceleration of gravity.
Further, in step S3, before the measurement, the efficiency p of the fixed pulley is measured, specifically, since the load output by the mechanical testing machine is not the real tension between the tenon joint nodes, the efficiency p of the fixed pulley is measured, the device for measuring the tension is fixed in the test piece slot and connected with the steel wire rope, then the device is loaded by the mechanical testing machine, and the tension values F of the mechanical testing machine are respectively read1And tension measured by the device for measuring tensionValue F2And calculating the efficiency p ═ F of the fixed pulley2/F1。
Further, the loading speed of the tester is 1-2 mm/min.
The invention has the beneficial effects that: the device and the method for measuring the friction coefficient of the tenon joint can realize quick, effective and accurate measurement of the friction coefficient of the tenon joint, are reasonable in structural design and convenient to operate, can effectively reduce measurement errors, enable the measurement errors to be in a minimum range, are low in cost and are beneficial to use. The device and the method for measuring the friction coefficient of the tenon joint can change the loading direction of a mechanical testing machine from a vertical direction to a horizontal direction; meanwhile, the preparation method of the piece to be tested is not limited to the elliptical tenon adopted in the invention, and other tenon joint forms are also applicable, so that the problem that the positive pressure of the tenon joint is difficult to measure is solved, and the tenon joint is converted into the known counterweight. The invention provides an effective method for the deep research of the tenon joint strength, and further lays a foundation for the structural design of wood structures and wood products.
Drawings
FIG. 1 is a schematic diagram illustrating a measurement method of friction coefficient by an electronic scale;
FIG. 2 is a schematic diagram illustrating the measurement of the friction coefficient by the existing jack method;
FIG. 3 is a schematic illustration of a prior art hydraulic cylinder method for measuring the coefficient of friction;
FIG. 4 is a schematic illustration of the preparation of a test piece on the side of the device for measuring the coefficient of friction of a tenon joint according to the embodiment of the present invention;
FIG. 5 is a schematic structural diagram of a device for measuring a coefficient of friction of a tenon joint according to an embodiment of the present invention;
FIG. 6 is a schematic view of the cross-sectional structure taken along line A-A of FIG. 5;
FIG. 7 is a schematic structural diagram of the friction coefficient measuring device of the tenon joint and the table top of the mechanical testing machine according to the embodiment;
FIG. 8 is a schematic top view showing a structure of a device for measuring a coefficient of friction of a tenon joint according to an embodiment;
wherein: 1-a tester interface, 2-a steering seat, 3-a fixed pulley, 4-a positioning interface, 5-a fixed bolt hole, 6-a fixed bolt, 7-a bottom plate, 8-a steel wire rope, 9-a to-be-tested piece, 10-a counterweight, 11-a test piece groove, 12-a rivet, 13-a steering groove, 14-a screw hole, 15-a positioning groove, 16-a table board of a mechanical tester, and 17-a positioning hole;
21-chassis, 22-steering block;
91-upper part of mortise, 92-lower part of mortise, 93-lateral tenon.
Detailed Description
Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
Examples
The utility model provides a measuring device of tenon joint node coefficient of friction, as fig. 5 and fig. 6, including bottom plate 7, wire rope 8, counter weight 10, test piece groove 11, steering mechanism and the testing machine interface 1 that is used for connecting the mechanics testing machine, the one end of bottom plate 7 is equipped with steering mechanism, the other end of bottom plate 7 is equipped with the test piece groove 11 that is used for holding test piece 9, counter weight 10 is located on test piece 9, test piece 9 is treated in wire rope 8's one end connection, wire rope 8's the other end is walked around steering mechanism and is connected testing machine interface 1.
This kind of measuring device of tenon joint node coefficient of friction can realize the swift effective accurate measurement of tenon joint node coefficient of friction, and structural design is reasonable, and the simple operation can effectively reduce measuring error for measuring error is in minimum scope, and the cost is lower, does benefit to the use. The measuring device for the friction coefficient of the tenon joint and the mechanical testing machine work in a cooperative mode, and the measuring precision is guaranteed.
In the device for measuring the friction coefficient of the tenon joint, the steering mechanism comprises a steering seat 2, a fixed pulley 3 and a fixed bolt hole 5, the steering seat 2 is provided with a steering groove 13, two ends of a rotating shaft of the fixed pulley 3 are respectively connected with two sides of the steering groove 13, and a steel wire rope 8 bypasses the fixed pulley 3 and is respectively connected with a piece to be tested 9 and a testing machine interface 1. By arranging the steering structure, the fixed pulley 3 realizes the conversion of the loading direction of the mechanical testing machine from the vertical direction to the horizontal direction.
In the device for measuring the friction coefficient of the tenon joint, as shown in fig. 5 and 8, the steering seat 2 comprises a chassis 21 and a steering block 22, the steering block 22 is arranged on the chassis 21, the steering block 22 is provided with a steering groove 13, the chassis 21 is provided with a fixing bolt hole 5 and a fixing bolt 6, the bottom plate 7 is provided with a screw hole 14, and the fixing bolt 6 penetrates through the fixing bolt hole 5 and the screw hole 14 of the bottom plate 7 to be in threaded connection with a bolt hole on the table board 16 of the mechanical testing machine. The chassis 21 is arranged to realize fixed connection with the bottom plate 7 and the mechanical testing machine, so that the steering mechanism and the bottom plate 7 are positioned. The bottom of bottom plate 7 is equipped with location interface 4, and the location interface plays the effect of location, location interface 4 and the locating hole adaptation on the mesa 16 of mechanics testing machine. Bottom plate 7 is equipped with constant head tank 15, and in constant head tank 15 was located to chassis 21, through the setting of constant head tank 15, the realization was to chassis 21's location, and then realized going on to steering mechanism's stable location, assurance measuring process's accuracy smoothly. The problem of measurement errors or errors caused by unnecessary movement of the steering mechanism during the measurement process is avoided.
In the device for measuring the friction coefficient of the tenon joint, as shown in fig. 4 and fig. 6, a to-be-tested part 9 comprises a to-be-tested tenon and a mortise component, the to-be-tested tenon is arranged in the mortise component, the mortise component comprises a tenon upper part 91 and a tenon lower part 92, the bottom surface of the tenon upper part 91 and the top surface of the tenon lower part 92 are butted to form a mortise together, the tenon upper part 91 and the mortise lower part 92 are respectively and independently arranged, the tenon upper part 91 is arranged on the tenon lower part 92, the tenon upper part 91 is connected with a steel wire rope 8, the tenon upper part 91 is fixedly connected with a counterweight 10, the tenon upper part 91 is not glued by a side tenon 93, and the tenon lower part 92 is glued by the side tenon 93.
The tenon hole component is divided into the tenon hole upper part 91 and the tenon hole lower part 92 which are independently arranged, and the bottom surface of the tenon hole upper part 91 and the top surface of the tenon hole lower part 92 are butted to form a tenon hole together, so that the accurate measurement of the friction coefficient of the tenon joint under the curved surface contact state can be realized.
In the device for measuring the friction coefficient of the tenon joint, the to-be-tested piece 9 adopts a double-tenon structure, namely, the to-be-tested piece 9 is provided with two groups of to-be-tested tenons and tenon hole components. By adopting the double tenon structure, the stability of the counterweight 10 at the time of loading can be ensured. The bottom plate 7 is made of metal plate or hard wood composite plate, and the accuracy of measurement is further ensured. The interface 1 of the testing machine is a standard interface, and the interface 1 of the testing machine is connected with a loading head of the mechanical testing machine.
A measuring method using the device for measuring a coefficient of friction of a tenon joint according to any one of the above methods, comprising the steps of,
s1, preparing a tested piece, respectively processing a lateral tenon 93 and a mortise component, as shown in FIG. 4, and cutting the mortise component into two parts from the middle part, namely, respectively obtaining a mortise upper part 91 and a mortise lower part 92, wherein the mortise lower part 92 is glued with the lateral tenon 93, so that the mortise lower part 92 and the lateral tenon 83 do not generate relative displacement when the steel wire rope 8 is subjected to tension loading, the mortise upper part 91 and the lateral tenon 93 are not glued, the mortise upper part 91 can freely slide under no pressure, and a rivet 12 is embedded in the mortise upper part 91 and is used for being connected with the steel wire rope 8;
s2, fixing the device for measuring the friction coefficient of the tenon joint according to any one of claims 1 to 5 with a mechanical testing machine through the positioning interface 4 and the fixing bolt hole 5, ensuring the bottom plate 7 to be horizontal, placing the glued lower part 92 of the tenon hole in the test piece groove 11, fixing, then butting and assembling the upper part 91 of the tenon hole and the lower part 92 of the tenon hole, and placing the counterweight 10 on the upper part 91 of the tenon hole and fixing the counterweight with the upper part 91 of the tenon hole; connecting the steel wire rope 8 with a rivet 12 on the upper part 91 of the mortise, and connecting the interface 1 of the testing machine with the testing machine;
s3, before measurement, measuring the efficiency p of the fixed pulley 3 for later friction coefficient calculation; during measurement, firstly, setting the loading speed of a testing machine; then, adjusting the testing machine to slowly tension the steel wire rope 8, observing the reading of the testing machine until the steel wire rope 8 is parallel to the bottom plate 7 and the reading of the tensile testing machine is zero, starting to measure to obtain the tensile force F displayed by the mechanical testing machine, and entering the next step;
in step S3, before the measurement, the efficiency p of the fixed pulley 3 is measured, specifically, since the load output by the mechanical testing machine is not the real tension between the tenon joint points, the efficiency p of the fixed pulley 3 is measured, a device for measuring the tension, such as a tension device or an electronic scale, is fixed in the test piece groove 11 and connected with the steel wire rope 8, and then the device is loaded by the mechanical testing machine, and the tension values F of the mechanical testing machine are respectively read1And the tension value measured by the device for measuring tensionF2And the efficiency p of the fixed pulley 3 is calculated to be F2/F1。
In the measuring process, the loading speed of the testing machine is not suitable to be too high, and the loading optimal speed of the mechanical testing machine is 1-2mm/min through tests, so that the measuring accuracy is ensured. During calculation of the friction coefficient, the self weight of the test piece is taken into consideration and cannot be ignored, so that the measurement accuracy is further ensured.
S4, calculating the friction coefficient mu of the tenon joint node as follows:
in the formula: f is the tensile force displayed by the mechanical testing machine; p is the efficiency of the fixed pulley 3; m is the weight 10 mass; m is the mass of the upper part 91 of the mortise; g is the acceleration of gravity.
The principle of the method for measuring the friction coefficient of the tenon joint is explained as follows, and the coulomb friction law is taken as the principle: and F is equal to mu N, the tensile force F can be measured by loading the testing machine, the positive pressure N can be calculated by the weight of the balance weight 10 and the upper part 91 of the tenon hole, and the friction coefficient mu of the tenon joint can be calculated.
According to the device and the method for measuring the friction coefficient of the tenon joint, the loading direction of a mechanical testing machine can be changed from the vertical direction to the horizontal direction by arranging the steering mechanism; meanwhile, the to-be-tested part 9 is not limited to the elliptical tenon adopted in the invention, other tenon joint modes are also applicable, and the embodiment device and the method solve the problem that the positive pressure of the tenon joint node is difficult to measure and convert the positive pressure into the known counterweight 10. An effective method is provided for the deep research of the tenon joint strength, and a foundation is further laid for the structural design of wood structures and wood products.
Claims (10)
1. A device for measuring the friction coefficient of a tenon joint is characterized in that: including bottom plate, wire rope, counter weight, test piece groove, steering mechanism and be used for connecting the testing machine interface of mechanics testing machine, the one end of bottom plate is equipped with steering mechanism, and the other end of bottom plate is equipped with the test piece groove that is used for holding the piece of waiting to test, and on the piece of waiting to test was located to the counter weight, the piece of waiting to test was connected to wire rope's one end, and steering mechanism connection testing machine interface was walked around to wire rope's the other end.
2. The apparatus for measuring a coefficient of friction of a mortise joint according to claim 1, wherein: the steering mechanism comprises a steering seat, a fixed pulley and a fixed bolt hole, the steering seat is provided with a steering groove, two ends of a rotating shaft of the fixed pulley are respectively connected with two sides of the steering groove, and a steel wire rope bypasses the fixed pulley and is respectively connected with a piece to be tested and a testing machine interface.
3. The apparatus for measuring a coefficient of friction of a mortise joint according to claim 2, wherein: the steering seat comprises a chassis and a steering block, the steering block is arranged on the chassis, the steering block is provided with a steering groove, the chassis is provided with a fixing bolt hole and a fixing bolt, the bottom plate is provided with a screw hole, and the fixing bolt penetrates through the fixing bolt hole and the screw hole of the bottom plate to be in threaded connection with the bolt hole on the table board of the mechanical testing machine.
4. A device for measuring the coefficient of friction of a mortise joint according to claim 3, wherein: the bottom of bottom plate is equipped with the location interface, location interface and the locating hole adaptation on the mesa of mechanics testing machine.
5. A device for measuring the coefficient of friction of a mortise joint according to claim 3, wherein: the bottom plate is provided with a positioning groove, the chassis is arranged in the positioning groove, and the bottom plate is made of a metal plate or a hardwood composite board.
6. The apparatus for measuring a coefficient of friction of a mortise joint according to any one of claims 1-6, wherein: the to-be-tested piece comprises a tenon to be tested and a tenon hole component, the tenon to be tested is arranged in the tenon hole component, the tenon hole component comprises a tenon hole upper portion and a tenon hole lower portion, the bottom surface of the tenon hole upper portion and the top surface of the tenon hole lower portion are butted to form a tenon hole together, the tenon hole upper portion and the tenon hole lower portion are arranged independently respectively, the tenon hole upper portion is arranged on the tenon hole lower portion, a steel wire rope is connected to the tenon hole upper portion, a counterweight is fixedly connected to the tenon hole upper portion, the tenon hole upper portion is not glued by a side tenon, and the tenon hole lower portion.
7. The apparatus for measuring a coefficient of friction of a mortise joint according to any one of claims 1-6, wherein: the piece to be tested adopts a double-tenon structure.
8. A measuring method using the device for measuring a friction coefficient of a mortise joint according to any one of claims 1 to 7, characterized in that: comprises the following steps of (a) carrying out,
s1, preparing a tested piece, respectively processing a side tenon to be processed and a tenon hole component, and cutting the tenon hole component into two parts from the middle part, namely respectively obtaining the upper part and the lower part of the tenon hole, wherein the mass of the upper part of the tenon hole is m, and the lower part of the tenon hole is glued with the side tenon to ensure that the lower part of the tenon hole and the side tenon to be processed do not generate relative displacement when the steel wire rope is subjected to tension loading, but the upper part of the tenon hole and the side tenon to be processed are not glued, so that the upper part of the tenon hole can freely slide under no pressure, and a rivet is embedded into the upper part of the tenon hole and is used for being connected with the steel wire rope;
s2, fixing the device for measuring the friction coefficient of the tenon joint node according to any one of claims 1 to 5 with a mechanical testing machine through a positioning interface and a fixing bolt hole, ensuring that a bottom plate is horizontal, placing the lower part of a glued tenon hole in a test piece groove, fixing, then butting and assembling the upper part of the tenon hole and the lower part of the tenon hole, and placing a balance weight with the mass of M on the upper part of the tenon hole and fixing the balance weight with the upper part of the tenon hole; connecting the steel wire rope with a rivet at the upper part of the mortise, and connecting an interface of the testing machine with the testing machine;
s3, before measurement, measuring the efficiency p of the fixed pulley, and calculating the friction coefficient in the later period; during measurement, firstly, setting the loading speed of a testing machine; then, adjusting the testing machine to slowly tension the steel wire rope, observing the reading of the testing machine until the steel wire rope is parallel to the bottom plate and the reading of the load of the mechanical testing machine is zero, starting to measure, moving the upper part of the tenon hole under the traction of the steel wire rope, recording the load value F displayed by the mechanical testing machine after the load is stable, and entering the next step;
s4, calculating the friction coefficient mu of the tenon joint node as follows:
in the formula: f is the tensile force displayed by the mechanical testing machine; p is the efficiency of the fixed pulley; m is a counterweight mass; m is the mass of the upper part of the tenon hole; g is the acceleration of gravity.
9. The method of measuring a coefficient of friction of a dovetail joint according to claim 8, wherein: in step S3, before measurement, the efficiency p of the fixed pulley is measured, specifically, since the load output by the mechanical testing machine is not the real tension between the tenon joint nodes, the efficiency p of the fixed pulley is measured, the device for measuring tension is fixed in the test piece groove and connected with the steel wire rope, then the device is loaded by the mechanical testing machine, and the tension values F of the mechanical testing machine are respectively read1And the tension value F measured by the tension measuring device2And calculating the efficiency p ═ F of the fixed pulley2/F1。
10. The method of measuring a coefficient of friction of a dovetail joint according to claim 9, wherein: the loading speed of the tester is 1-2 mm/min.
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| CN111811964A (en) * | 2020-07-16 | 2020-10-23 | 内蒙古农业大学 | Wood structure mortise and tenon joint loading test device and method |
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